[sc_rufctr]

These are cool. They came in a few different versions and configs.
From memory the early ones had an unusual 2.5mm (or was it 3.5mm?) Allen head bolt to secure the cable inside.

They're aerodynamically "cleaner" than traditional brakes but they do weight a little bit more.
Because of this they were often used for time trial bikes.

$350USD is the right sort of money for these.
The "Record" version (hidden springs at the rear) can go for upwards of $650 USD depending on condition. A full set new in the box? Over a grand easy.

Not that long ago I saw a pair of "black" prototypes in a Melbourne bike shop. Asking $5,550AUD just the brakes... No levers, cables, pads or box.

If they were mine I'd be hanging onto them.